With Complexity, Decks Are Stacked

Ron McClamrock teaches the philosophy of science at the University of Albany, SUNY.

Originally in Newsday, February 3, 2003

Almost before the mourning, the search for the explanation begins.
When a public disaster like Saturday's space shuttle crash takes
place, it's our natural impulse to find out why - an impulse motivated
largely by a desire to avoid such tragedies in the future and to learn
from our mistakes. Was it tiles damaged at takeoff? The wrong angle at
rollover? A fuel leak? Insufficient funding?

Sometimes, this search can slide from inquiry to inquisition, and
from putting our finger on answers to pointing it in accusation or
blame. We surely don't know what happened now; perhaps, through the
painstaking examination of debris and data, we will be able to trace
the chain of events that happened Saturday morning, 200,000 feet above
the southwest United States. We like our answers to these questions to
be simple and unified. But in cases like this one, in the complex and
unknown region at the boundaries of what we can do, they might well
turn out to be neither.

In general, as systems get more complex, they tend also to become
more susceptible to tiny failures. A pile of cards can have one pulled
out without significant consequence, but a house of cards, where each
does a particular job, is far less resilient. And in a highly complex
system, those small failures can easily snowball into large-scale
failures. Take computers, where a single "1" instead of "0" can mean
the difference between crashing and working.

The shuttle is, of course, the epitome of complexity: 2.5 million
parts, including the 27,000 tiles that protect against the heat of
re-entry, combined with the almost unimaginable extreme conditions of
speeds more than 17,000 miles per hour and temperatures of 2,800
degrees Fahrenheit, give us exactly the kind of situation where what
works on paper has the least guarantee of working in practice. The
tiniest variations may have the most profound effects. And without
significant real-world experience, we won't know which of those tiny
variations will occur, or which will have profound effects - a tile
here or there, a degree or two of approach alignment, or, as with the
Challenger in 1986, a slight drop in the temperature of the O-rings.

Surely there's a cautionary tale here about taking for granted our
complex technologies - the shuttle, or more mundanely, the Internet or
nuclear power. But before we rush to a Luddite's conclusion, it's
important to see that this isn't just about technology. It's a general
fact about complexity, and not just a particular problem for
complicated mechanisms that we might build. Nearly every moment of our
everyday lives rests on such delicate not-quite-catastrophes.

Consider natural systems, like the human body. It's part of the
nature of complex interdependent biology that different jobs are done
by different tiny parts of the system, and that those parts can be
vulnerable to small problems, which can then amplify into large ones.
The delicate subtlety required for the normal functioning of cells is
also what makes them vulnerable to viruses.

In fact, it's in our natural world where the delicate balances are
often the most difficult to grasp - for example, understanding the
fragile balance of normal cellular life and growth that straddles the
catastrophe of cellular death on one hand, and uncontrolled cancerous
cellular multiplication on the other. In the end, we can't really
avoid these delicate and sometimes catastrophic balancing acts,
although we can sometimes manage and minimize them. And technology is
sometimes the route to minimizing those catastrophes in both
occurrence and consequence, as in much of modern medicine.

Our lives, and not just those of the shuttle crew, are often
balanced on such chaos, as in the line between normal cell growth and
cancer. We can't avoid all this by pulling back from technology. It
assaults us all the time, even in our mundane lives. We're perched on
precarious bits of marginally stable chaos that are surrounded by
catastrophe, like a house of cards - cells and cancer, the working of
the brakes on the truck behind us, and so on. The fragility of our
lives and world might be managed, but never eliminated.

When we extend our reach, as with the space program, the
uncertainties and complexities multiply, and the fragility of it all
comes to the surface again. And whatever concrete explanation we may
find in the months to come, we should not make the mistake of thinking
we have made this activity completely safe. Let us not forget again,
as we did before the Challenger in 1986 and perhaps had begun to do
again, that the people who go up are test pilots, shouldering the
risks for the rest of us in the worthwhile quest to expand the
frontiers of knowledge.